Boris Johnson's campaign to position himself as the natural successor to David Cameron has received a big boost from a poll showing he is Britain's most respected political figure – outstripping even Margaret Thatcher.

The YouGov poll, showing the London mayor is respected by 58% of voters compared with 46% for Thatcher, will be welcomed by Johnson because it appears to answer one of the main criticisms voiced in private in No 10: that he is a showman who cannot command respect as a heavyweight politician.

Johnson's emphatic lead over Thatcher will be of symbolic significance, even though she retired 22 years ago, because Britain's first woman prime minister is still revered by Tory activists who have the final say in any leadership contest.

The YouGov poll for this week's Cambridge conference, at which the Guardian is the media partner, is published as the Johnson prepares to use next month's Tory conference to maintain the momentum from his high-profile summer. He is comfortably ahead of Cameron, his Eton and Oxford contemporary, who is respected by 37% of voters. George Osborne, the mayor's junior in age and most likely rival for the Tory leadership, trails Johnson on 16%.

Downing Street is dismissive of the threat posed by Johnson, who overshadowed Cameron with a witty speech at the Olympics and Paralympics victory parade on Monday. No 10 sources said serious times called for serious people.

But Johnson's allies say his success in winning two consecutive mayoral contests in a predominantly Labour city show he has the appeal that could secure the prize that has, so far, eluded Cameron – winning an overall Conservative parliamentary majority. Johnson's case will be strengthened by the You-Cambridge conference poll, at which the Guardian is media partner.

The poll shows that while Johnson's appeal is strongest in the south of England, his popularity reaches most parts of the country, except for Scotland. In the Midlands and northern England, for example, he is respected by 55% and 53% of the population, respectively. He enjoys respectful majorities, too, across social classes and gender, and in every age group except for the youngest.

Johnson enjoys a commanding lead over 19 heavyweight political figures featured in the poll. He has an overall net score on respect of +25 points. This is calculated by subtracting the proportion who extend little or no respect to each of the figures from the proportion that respects them a great deal or a fair amount.

The only other political figure with a positive net score is Thatcher, on +1.

William Hague, the foreign secretary who is rapidly emerging as the "under the bus" candidate to succeed Cameron if the prime minister were to leave office abruptly, has the highest net score of any serving parliamentarian. Hague scores -1 point.

George Galloway, the founder of the Respect party, ironically appears to be Britain's least respected politician. His overall net respect score is -67 points.

The mayor is so popular he is within sight of Lord Coe, the double Olympic gold medallist who chaired the organising committee for London 2012. On the separate question of favourability, Coe has a net popularity rating of +29 compared with +26 for the mayor. But Johnson has a long way to go to catch the Olympic champions Jessica Ennis (+67) and Mo Farah (+66) – and the Queen (+58).

The poll makes uncomfortable reading for Osborne. The chancellor's net respect score among Tory voters is -14 points compared with +69 for Johnson. Only 13% of voters believe the chancellor is doing a good job compared with 60% who believe he is doing a bad job. More than half of those asked (57%) believe Osborne should be replaced while 17% believe he should remain.

The poll follows the YouGov/Sun poll on Wednesday, which found that the Tories would achieve a six-point poll bounce if Johnson were to replace Cameron as Tory leader.It found the Tories would increase their share from 31% to 37% if Johnson became leader. Labour would fall from 42% to 38%, thereby reducing the party's 11 point lead to a single point.

Johnson's popularity is highlighted in other YouGov findings released this week which show he is a long way ahead of the three main party leaders on a series of key characteristics. More than half of voters (56%) regard Johnson as charismatic, compared with 21% for Cameron, 3% for Miliband and 11% for Clegg.

Downing Street's claim that Johnson is not a serious figure will be challenged by some of the findings. Nearly a third of voters (29%) believe Johnson sticks to what he believes in compared with 19% for Cameron, 18% for Miliband and 7% for Clegg.

Johnson is using the prospect of a third runway at Heathrow airport to differentiate himself from Cameron. The London mayor says he is standing by the Tory opposition to a third runway and was highly critical of the prime minister's decision to demote the former transport secretary Justine Greening amid signs that the Tories are preparing to embark on a U-turn.

Just over a quarter (26%) of voters regard Johnson as strong, compared with 11% for Cameron, 5% for Miliband and 3% for Clegg. Johnson is ahead of Cameron (25% to 6%) when voters were asked who was in touch with ordinary people.

The poll findings come as a small, but determined, group of Tory MPs try to oust Cameron. The Spectator reported this week that 14 Tory MPs have written letters to Graham Brady, chairman of the 1922 committee, calling for a leadership contest. This falls a long way short of the 46 letters needed to trigger a contest.

Between 11 and 12 September 2012, YouGov questioned 1,703 GB adults, and asked the questions about "respect". Other questions quoted come from a slightly earlier survey – between 9 and 10 September 2012 YouGov questioned 1,871 GB adults. The surveys were carried out online. All figures have been weighted and are representative of all GB adults (aged 18+)

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